Health Guide
How to Calculate BMI: Complete Guide for 2026
What is BMI?
Body Mass Index (BMI) is a simple calculation that uses your height and weight to estimate body fat. While it doesn't directly measure body fat, it's a useful screening tool for weight categories that may lead to health problems.
The BMI Formula
Metric formula: BMI = weight (kg) ÷ height² (m²)
Imperial formula: BMI = weight (lbs) × 703 ÷ height² (in²)
Example Calculation
A person weighing 70 kg with a height of 1.75 m:
BMI = 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9
A BMI of 22.9 falls in the "Normal weight" range.
BMI Categories
| Category | BMI Range |
|---|---|
| Underweight | Below 18.5 |
| Normal weight | 18.5 – 24.9 |
| Overweight | 25.0 – 29.9 |
| Obese (Class I) | 30.0 – 34.9 |
| Obese (Class II) | 35.0 – 39.9 |
| Obese (Class III) | 40.0 and above |
Limitations of BMI
BMI doesn't account for muscle mass, bone density, body composition, or fat distribution. Athletes may have a high BMI despite low body fat. Use BMI as a starting point, not a diagnosis. For a more complete picture, try our Overall Health Score.
Related Calculators
- BMI Calculator — Calculate your BMI instantly
- Body Fat Calculator — Measure body fat percentage
- Ideal Weight Calculator — Find your healthy weight range
- Overall Health Score — Complete health assessment